Fluorescent ink detector

ABSTRACT

A printer luminescent ink sensor for a printing device including a radiant energy source; and a photodetector located downstream from a print head of the printing device. The photodetector is adapted to detect luminescent energy from an indicium printed by the print head, upon exposure to radiant energy from the radiant energy source, substantially immediately after the indicium is printed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to printing and, more particularly, todetecting in a printing device the printing of a luminescent ink.

2. Brief Description of Prior Developments

Currently there is no way for a postage meter to determine if afluorescent ink is being used in a postage meter. Furthermore, there isno way of identifying if either a fluorescent ink is printed or if afluorescent ink indicium is missing due to a mechanical/electricalproblem with the print head. It is important for a postage metermanufacturer to be aware of any of these outcomes to warrant that itsmeters operate as designed. Any solution to these problems must also besmall enough to be implemented in mailing machines. There aresophisticated instruments, unrelated to printers or postage meters,which can give a fluorescent spectral response, but these instrumentsare very large and expensive.

Currently many postage meter manufacturers place microchips on their inkcartridges to prevent the printer (or meter) from printing with acounterfeit or wrong ink color cartridge. This protects the integrity ofthe equipment and prevents the printer from being damaged by counterfeitink. These chips have to be placed on each of the millions of cartridgesproduced, and are a significant expense. There is a desire to provide analternative way of solving this problem. There is a desire to provide aRead After Print (RAP) sensor to protect supplies revenue and preventdamage to postage meters from unauthorized ink usage.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, a printerluminescent ink sensor for a printing device is provided including aradiant energy source; and a photodetector located downstream from aprint head of the printing device. The photodetector is adapted todetect luminescent energy from an indicium printed by the print head,upon exposure to radiant energy from the radiant energy source,substantially immediately after the indicium is printed.

In accordance with another aspect of the present invention, a printerfluorescent ink sensor for a printing device is provided comprising aradiant energy source; and a system for determining quality offluorescence of an indicium printed by a print head of the printingdevice. The system comprises a fluorescent ink photodetector locateddownstream from the print head.

In accordance with one method of the present invention, a method ofprinting luminescent ink in a printing device is provided comprisingprinting an indicium on an article at a print head of the printingdevice; radiating energy towards the printed indicium; and detectingenergy emitted by the indicium at a sensing location in the printingdevice downstream of the print head.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and other features of the present invention areexplained in the following description, taken in connection with theaccompanying drawings, wherein:

FIG. 1 is a diagram showing some components of a postage meterincorporating features of the present invention;

FIG. 2 is a chart showing of signals sent by the photodetector to thecontroller of FIG. 1 when the indicium being read is properly printedusing red fluorescent ink;

FIG. 3 is a chart showing signals sent by the photodetector to thecontroller of FIG. 1 when the indicium being read is properly printedusing black fluorescent ink;

FIG. 4 is a chart showing signals sent by the photodetector to thecontroller of FIG. 1 when the indicium being read is printed usingnon-fluorescent ink or not properly printed using fluorescent ink;

FIG. 5 is a diagram showing some components of a postage meter of analternate embodiment of the present invention;

FIG. 6 is a chart showing a signal sent by a first sensor of thephotodetector of FIG. 5 to the controller of the postage meter;

FIG. 7 is a chart showing signal sent by a second sensor of thephotodetector of FIG. 5 to the controller;

FIG. 8 is a chart showing signal sent by a third sensor of thephotodetector of FIG. 5 to the controller;

FIG. 9 shows a chart of a fluorescence spectra of intensity versuswavelength for a first fluorescent ink;

FIG. 10 is a chart which illustrates a signal from a firstlight-to-voltage sensor with a 615 nm filter when reading indiciumprinted with the ink of FIG. 9;

FIG. 11 is a chart which illustrates a signal from a secondlight-to-voltage sensor with a 500 nm filter when reading indiciumprinted with the ink of FIG. 9;

FIG. 12 shows a chart of a fluorescence spectra of intensity versuswavelength for a second fluorescent ink;

FIG. 13 is a chart which illustrates a signal from a firstlight-to-voltage sensor with a 615 nm filter when reading indiciumprinted with the ink of FIG. 12; and

FIG. 14 is a chart which illustrates a signal from a secondlight-to-voltage sensor with a 500 nm filter when reading indiciumprinted with the ink of FIG. 12.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, there is shown a diagram of some components of apostage meter 10 incorporating features of the present invention.Although the present invention will be described with reference to theexemplary embodiments shown in the drawings, it should be understoodthat the present invention can be embodied in many alternate forms ofembodiments. In addition, any suitable size, shape or type of elementsor materials could be used.

The postage meter 10 generally comprises a print head 12, a printerluminescent ink sensor 14, and a controller 16. The postage meter 10preferably comprises other features such as a display, an input device,and a data communications device (such as a modem), not shown. Althoughthe present invention is being described with reference to use in apostage meter, features of the present invention could be used in anysuitable type of printing device which is adapted to print an indiciumwith luminescent ink, such as fluorescent ink or phosphorescent ink.

The print head 12 is adapted to print a postage indicium 18 on anarticle 20, such as an envelope or an adhesive paper strip. The printhead 12 uses an ink jet printing method. The ink used to print theindicium 18 preferably comprises fluorescent ink. Color fluorescentinks, including black fluorescent ink, are known such as described inU.S. patent application publication Nos. US 2002/0195586 A1, US2003/0005303 A1, and US 2003/0041774 A1, which are hereby incorporatedby reference in their entireties. The color fluorescent ink could be anysuitable color including, for example, red or blue. Invisible ink jetinks are also described in U.S. patent application Ser. No. 10/331829filed Dec. 30, 2002 which is also hereby incorporated by reference inits entirety. Use of fluorescent inks for hidden indicium is describedin U.S. patent application Ser. No. 10/692,569, filed Oct. 24, 2003,(attorney docket No. F-736) which is also hereby incorporated byreference in its entirety.

Luminescent ink, such as fluorescent ink, can be used by a governmentpostal service, such as the U.S. Postal Service (USPS), to validate orconfirm that a postage indicium is authentic. The luminescent ink canalso be used to place a marking on a postage indicium by the postalservice to indicate that the postage value has been used or consumed. Asnoted above, in the past there was no way for a postage meter todetermine if fluorescent ink was being used in the postage meter.Furthermore, there was no way of identifying in the postage meter itselfif either a fluorescent ink was printed, or if a fluorescent inkindicium was missing or incomplete due to a mechanical/electricalproblem with the print head.

The present invention comprises the sensor 14 to overcome theseproblems. The sensor 14 is located downstream from the print head 12. Inother words, as the article 20 moves in direction 28, the indicium 18 isprinted by the print head and then moves along a sensing location 30 atthe sensor 14. The sensor 14 generally comprises a photodetector 22 anda radiant energy source or excitation source 24. The photodetector 22generally comprises a light-to-voltage sensor. However, any suitabletype of photodetector could be used. The radiant energy source 24generally comprises an ultraviolet (UV) light emitting diode (LED). TheLED comprises a 410 nm LED. However, any suitable type of radiant energysource could be used. The sensor 14 also comprises a filter 26. Thefilter 26 is a wavelength filter, such as a 550 nm high pass filter.However, any suitable filter could be provided whether it be a physicalfilter or a coating on the optical lens. The filter is located in frontof the light-to-voltage sensor, between the light-to-voltage sensor andthe indicium 18.

By using an ultraviolet (UV) light emitting diode (LED) and a detectionsystem located downstream from the print head, the postage meter candetermine the type of ink (fluorescent or non-fluorescent) that wasprinted on the envelope. The postage meter can use this information towarn the user of problems with the ink supply or if the wrong ink hasbeen used. These are problems which can now be addressed by the drop incost of detector components (UV LED, phototransistors).

Referring also to FIGS. 2-4, charts are shown of signals sent by thephotodetector 22 to the controller 16. FIG. 2 illustrates a signalpattern when the indicium 18 is properly printed using red fluorescentink. FIG. 3 illustrates a signal pattern when the indicium 18 isproperly printed using black fluorescent ink. FIG. 4 illustrates asignal pattern when the indicium 18 is properly printed usingnon-fluorescent ink or when the indicium is not properly printed withfluorescent ink. The voltage outputs from the photodetector can besummarized as follow: Output Ink Type   1 V-2 V Red Fluorescent Ink 0.5V-1 V Black Fluorescent Ink Less than 0.5 V Non-Fluorescent Ink (orinsufficient fluorescent ink)

A method for producing a small, low cost, fluorescence detection systemcan be provided to identify:

-   -   a fluorescent ink type or that a non-fluorescent ink type was        printed; and/or    -   that the print head is functioning properly; and/or that a good        print (good quality fluorescent indicium) was made.

With a low cost device (the sensor 14), such as less than $10.00, themeter can determine if the ink used to print the indicium 18 isfluorescent or not right after printing of the indicium 18 by the printhead 12. If the sensor 14 detects that the indicium 18 is not properlyprinted (such as with insufficient fluorescent ink), or was printedwithout fluorescent ink, the meter can display an error message and warnthe user to obtain the ink needed. Additionally, this sensor system canvalidate the indicium and insure there is enough fluorescence in theindicium 18 for the mail piece 20 to be faced by a USPS Facer-Cancellersystem.

This invention can consist of an ultraviolet light emitting diode(UV-LED), a wavelength filter (such as a 550 nm or 600 nm high passfilter for example), and a light-to-voltage sensor. The UV-LED 24 canprovide 410 nm light energy to the printed indicium. The indicium 18, iffluorescent, can transform the UV light 32 into 600 nm orange light. Thelight-to-voltage sensor 22, fitted with a special filter 26, can absorb(detect) 600 nm light and convert it to an output voltage. If softwarein the postage meter does not detect this voltage spike, the meter canreport an error; signaling no print or printing with the wrong ink orinsufficient fluorescent ink.

With a given ink, the expected voltage change is consistent and known.The shape of the waveform outputted by the light-to-voltage sensor canbe analyzed. Any change in the magnitude of the waveform outside the setparameters (more or less fluorescence) can indicate that a different ink(unapproved ink or competitor ink) is in use, or that there has been aprint head failure. If differences in the width of the waveform peaks(such as the peaks shown in FIGS. 2 and 3) are detected, it can indicatethat the print head nozzles may be clogged and that a full print is notbeing achieved.

Referring now also to FIGS. 5-8, postage meter 40 with a system andmethod can be provided for producing a small, low cost, fluorescencedetection system to identify unique spectral characteristics of aparticular ink. This can consist of an ultraviolet light emitting diode(UV-LED) 24, a set of filters 26, 34, 36 with different narrow bandpasswavelengths or different transmission rates, and severallight-to-voltage sensors 22. The UV-LED 24 can provide 410 nm lightenergy to the printed indicium 18. The indicium 18, if fluorescent, cantransform the UV light 32 into a longer wavelength fluorescent emission.The light-to-voltage sensors 22 can be fitted with special filters 26,34, 36 that will absorb (detect) fluorescent light and convert it to anoutput voltage. Each light-to-voltage sensor 22 can look forfluorescence in a different wavelength region. Thus, multiple detectorscan be used to build a complex (multiple) and perhaps completefluorescent spectra of the ink used in the indicium. Additionally, aninfrared (IR) detector 42 can be added to detect the presence of blackpigments in the ink.

In the diagram of FIG. 5 narrow bandpass filters 26, 34, 36 of 400 nm,500 nm and 620 nm are used to obtain the fluorescent intensity at thatwavelength. However, in alternate embodiments more or less than threefilters and light-to-voltage sensors could be used. In addition, thefilters could have any suitable bandpass. FIG. 6 illustrates a signalfrom the first 1 light-to-voltage sensor 22 with first filter 26 whenreading the indicium 18. FIG. 7 illustrates a signal from the second 2light-to-voltage sensor 22 with second filter 34 when reading theindicium 18. FIG. 8 illustrates a signal from the third 3light-to-voltage sensor 22 with third filter 36 when reading theindicium 18.

In one type of embodiment, the photodetector could have a minimumdetection threshold which can be set to give a discrete value for aparticular ink or fluorescence wavelength, such as detection thresholds44, 46 and 48 shown in FIGS. 6-8. If the ink is above the threshold itcan be assigned a value of “1”. If the ink is below the threshold it canbe assigned a value of “0” (i.e. 0, 1, 1 for the illustration in FIGS.5-8). Other types of fluorescent ink can have a digital signal of 1,0,0;or 1,1,0; etc. Thus, the photodetector can differentiate betweendifferent fluorescent inks by the use of multiple photosensors; eachadapted to sense a different wavelength. A non-fluorescent ink wouldhave no fluorescence and would give a value of zero on all threedetectors 22 (0,0,0). This can be extended to include multiple detectorsand give further differentiation between inks.

There are no commercially available products that specifically detectred fluorescent emissions. Spectrophotometers and the like areavailable, but cost tens of thousands of dollars. The current inventioncan cost less than $10.00 to produce. This invention can compriseplacing a multiple detector system (2 or more light detectors) on apostage meter or a printer itself. The sensing system can determinemultiple spectra characteristics of the ink's spectra that was printed.This enables software in the postage meter or printer to determine whichink has been printed, and can display an error message if the wrong inkis installed, or insufficient ink was used to print the indicium, or ifthe wrong ink was used. Also, by using a UV LED and a detection systemlocated downstream from the print head, the postage meter or fluorescentink printer can determine the type of ink (fluorescent, non-fluorescent,or black pigment based) that was printed on the article 20. The postagemeter or printer can use this information to warn the user of problemswith the ink supply or if the wrong ink has been used, such as bydisplaying an error message on the display and/or making an audiblesound.

Referring now also to FIGS. 9-11, FIG. 9 shows a fluorescence spectra ofintensity versus wavelength for a first fluorescent ink 50. In thisembodiment the ink 50 comprises a red fluorescent ink sold by thepostage meter manufacturer. A system could be provided with only twophotosensors; such as one with a 615 nm filter and one with a 500 nmfilter. FIG. 10 illustrates a signal pattern from a firstlight-to-voltage sensor 22 with a 615 nm filter when reading theindicium 18 printed with the ink 50. FIG. 11 illustrates a signalpattern from a second light-to-voltage sensor 22 with a 500 nm filterwhen reading the indicium 18 printed with the ink 50. Again, using thedetection thresholds 47, 46, the output from the photodetector would be1,0 when reading an indicium printed with the red fluorescent ink 50.

Referring now also to FIGS. 12-14, FIG. 12 shows a fluorescence spectraof intensity versus wavelength for a second fluorescent ink 52. In thisembodiment the ink 52 comprises a red fluorescent ink sold by athird-party to the postage meter manufacturer. The postage meterphotodetector system, reading an indicium printed with the third-party'sink 52 would produce the outputs shown in FIGS. 13 and 14 for its twodetectors of 0,1.

Because the controller did not sense a 1,0 signal after reading theindicium, the controller can automatically determine that anunauthorized ink is being used in the postage meter. The postage metercan be programmed to perform any one of a number of different actionsbased upon this reading. This can include, for example, disabling thepostage meter until a service technician can be called, displaying amessage on the display of the postage meter (such as the ink isunauthorized or replace the ink cartridge with a proper ink cartridge),activate a communications system to send a message to the postage metermanufacturer that a third party's ink is being used (so the manufacturercan offer a discount pricing to the user to attempt to keep the user asa customer), signal a patent infringement, or signal a violation ofpostal codes. Of course, these are only examples. Other uses offluorescent or luminescent ink determination and/or differentiationcould be incorporated into the postage meter or fluorescent ink printer.

It should be understood that the foregoing description is onlyillustrative of the invention. Various alternatives and modificationscan be devised by those skilled in the art without departing from theinvention. Accordingly, the present invention is intended to embrace allsuch alternatives, modifications and variances which fall within thescope of the appended claims.

1. A printer luminescent ink sensor for a printing device comprising: aradiant energy source; and a photodetector located downstream from aprint head of the printing device, wherein the photodetector is adaptedto detect luminescent energy from an indicium printed by the print head,upon exposure to radiant energy from the radiant energy source,substantially immediately after the indicium is printed.
 2. A printerluminescent ink sensor as in claim 1 wherein the radiant energy sourcecomprises an ultraviolet (UV) light emitting diode (LED).
 3. A printerluminescent ink sensor as in claim 1 wherein the photodetector comprisesa light-to-voltage sensor.
 4. A printer luminescent ink sensor as inclaim 3 wherein the photodetector comprises a wavelength filter.
 5. Aprinter luminescent ink sensor as in claim 4 wherein the wavelengthfilter comprises about a 550 nm high pass filter.
 6. A printerluminescent ink sensor as in claim 1 wherein the photodetector comprisesa plurality of photosensors, wherein at least two of the photosensorsare adapted to detect different wavelengths.
 7. A printer luminescentink sensor as in claim 6 wherein two of the photosensors each comprise alight-to-voltage sensor and a different bandpass wavelength filter.
 8. Aprinting device comprising: a print head; a system for determining printquality of a printed indicium printed by the print head on an article,the system comprising: a printer luminescent ink sensor as in claim 1located downstream from the print head; a system for determining if theprinted indicium comprises luminescent ink based upon a signal from theprinter luminescent ink sensor.
 9. A printing device as in claim 8wherein the printing device comprises a postage meter and the print headcomprises a postage meter print head.
 10. A printing device as in claim8 wherein the system for determining print quality is adapted todetermine if the printed indicium comprises a minimum predeterminedamount of luminescence.
 11. A printing device as in claim 8 wherein thesystem for determining print quality is adapted to determine a qualityof the printed indicium based upon a shape of a waveform signal from theprinter luminescent ink sensor.
 12. A printing device as in claim 8wherein the system for determining print quality is adapted todifferentiate between different inks.
 13. A printing device as in claim12 wherein the system for determining print quality is adapted todifferentiate between different fluorescent inks.
 14. A printing deviceas in claim 8 further comprising an infrared (IR) detector adapted tosense black ink pigments.
 15. A printing device as in claim 8 whereinthe photodetector is adapted to sense at least two separate wavelengthsand adapted to output a digital value based upon a detection thresholdfor each of the wavelengths.
 16. A printing device as in claim 15wherein the photodetector comprises a plurality of light-to-voltagesensors and a different filter with different transmission rates at eachlight-to-voltage sensor.
 17. A printer fluorescent ink sensor for aprinting device comprising: a radiant energy source; and a system fordetermining quality of fluorescence of an indicium printed by a printhead of the printing device, the system comprising a fluorescent inkphotodetector located downstream from the print head.
 18. A printerfluorescent ink sensor as in claim 17 wherein the radiant energy sourcecomprises an ultraviolet LED.
 19. A printer fluorescent ink sensor as inclaim 17 wherein the photodetector comprises a light-to-voltage sensorand a wavelength filter.
 20. A printer fluorescent ink sensor as inclaim 17 wherein the photodetector comprises a plurality ofphotosensors, wherein at least two of the photosensors are adapted todetect different wavelengths.
 21. A printer fluorescent ink sensor as inclaim 17 wherein two of the photosensors each comprise alight-to-voltage sensor and a different bandpass wavelength filter. 22.A printing device comprising: a print head; a printer fluorescent inksensor as in claim 17 located downstream from the print head furthercomprising a system for determining if the indicium comprisesfluorescent ink based upon a signal from the printer fluorescent inksensor.
 23. A printing device as in claim 22 wherein the printerfluorescent ink sensor is adapted to determine if the indicium comprisesa minimum predetermined amount of fluorescence.
 24. A printing device asin claim 22 wherein the printer fluorescent ink sensor is adapted todetermine a quality of the indicium based upon a shape of a waveformsignal from the printer fluorescent ink sensor.
 25. A printing device asin claim 22 wherein the printer fluorescent ink sensor is adapted todifferentiate between different inks.
 26. A printing device as in claim25 wherein the printer fluorescent ink sensor is adapted todifferentiate between different fluorescent inks.
 27. A printing deviceas in claim 22 further comprising an infrared (IR) detector adapted tosense black ink pigments.
 28. A printing device as in claim 22 whereinthe photodetector is adapted to sense at least two separate wavelengthsand adapted to output a digital value based upon a detection thresholdfor each of the wavelengths.
 29. A printing device as in claim 28wherein the photodetector comprises a plurality of light-to-voltagesensors and a different filter with different transmission rates at eachlight-to-voltage sensor.
 30. A printing device as in claim 22 whereinthe printing device comprises a postage meter and the print headcomprises a postage meter print head.
 31. A method of printingluminescent ink in a printing device comprising: printing an indicium onan article at a print head of the printing device; radiating energytowards the printed indicium; and detecting energy emitted by theindicium at a sensing location in the printing device downstream of theprint head.
 32. A method as in claim 31 wherein the printing devicecomprises a postage meter, and printing of the indicium comprisesprinting a postage indicium on an article.
 33. A printer fluorescent inksensor as in claim 17 wherein the photodetector comprises aphototransistor including a band-pass filter.